1. Field of the Invention
The present invention generally relates to an apparatus for controlling an electric clothes dryer, and particularly relates to an apparatus for performing controlling an electric clothes dryer so that a temperature at a respective portion of the electric clothes dryer is prevented from abnormally rising in the case where a voltage of a power source connected to the dryer exceeds a rated value thereof.
2. Description of the Related Art
Generally, in an electric clothes dryer, a current is caused to flow in an electrical heater to generate heat and air is heated by the thus generated heat to be applied onto clothes in a drum by using a fan so as to dry the clothes. In such a dryer as described above, a capacity of the heater for obtaining a predetermined clothes drying performance (ordinarily, represented by the weight of clothes which can be dried once) is determined, and if a resistance value of the heater is fixed once on the basis of the desired capacity of the heater, the electric power consumed by the heater is increased in proportion to a square of a voltage applied thereto as the voltage rises.
Generally, a voltage of a commercial power source line may fluctuate by .+-. several %, or .+-. over ten % in an extreme case, of the rated value thereof, and therefore also the power consumption in a heater, that is, a calorific value thereof varies in accordance with the voltage fluctuation. For example, when a heater is supplied with a voltage of 110% of a rated value thereof, a calorific value of the heater becomes a value of 1.21 times as large as that in the case of supplying the rated voltage. In such a case where the line voltage rises in the electric clothes dryer of the type as described above, therefore, the temperatures at portions in the surrounding of the heater and at portions to which hot air is applied become considerably high. Accordingly, if the capacity of the heater, and the respective dimensions and shapes of parts of the dryer are determined on the assumption that the rated voltage of the dryer does not rises, the temperature at the parts inside the dryer and at the clothes to be dried may abnormally rise in the case where the line voltage exceeds the rated value, resulting in a danger that the parts and the clothes may be damaged.
As measures to cope with such a rising in supply voltage as described above, there have been proposed a method in which the dryer is previously made to have air blowing capacity of the fan enough to large capable for increasing temperature due to voltage rise, a method in which gaps between a heater and parts disposed in the surrounding of the heater are made larger, a method in which a heater having a smaller surface power density is used, and so forth. In any method, the heater and the constituent parts are designed with an allowance in advance on the assumption that the supply voltage may rise higher than the rated value. In this case, there has been problems in manufacturing the dryer in that the shape of the dryer per se becomes larger than that in the case where the dryer is designed on the assumption that the supply voltage does not exceed the rated voltage, resulting in increase in cost of the dryer. Further, even if any one of the foregoing methods could cope with the rising in supply voltage so that the temperature rising in the parts of the dryer does not reach an abnormal value in the case where the supply voltage rises to a certain value, there is a possibility that when the dryer is used in a different commercial voltage zone, the dryer may exceed in quality relative to a requirement therefore, or, conversely, an abnormally high temperature may be generated.